Joomla 4 issue preparing content

In Joomla 3 I had set up a nice managed video system using Joomla component content category, and in each article I simply put:

[cbgallery:gallery /]

This worked great in J3 to have a separate gallery for each article in the target category.  Now in J4 I notice it is randomly not processing that line. It just shows the line above instead of the gallery.  When I forced a page reload ( desktop Firefox ) it would work, but obviously I need it to always work regardless of cache.

Is this a magic new "feature" of Joomla 4 I don't know about?
 

Can't see any reason within the plugin for it self to suddenly stop working unless something prevented it from loading. Are you using caching within Joomla? If so try disabling it and see if the issue goes away.

I already had cache turned off - altho despite that it appears to be caching page views sometimes. But today, no cache and my first visit to the article again did not process cbgallery. I hit reload a dozen times but no difference. I had on debug and I captured some output in attached "bad.txt".  Then I did force reload and it worked like it was supposed to. I attach that debug output in "good.txt".  You can clearly see it processing gallery tables in good but not bad.  
The regular reload of course is pulling the page from Firefox's own cache, and the force reload invalidates that cache and requires the webserver to resend it. But why is J4 sending the wrong version the first time?

Browsers don't cache text unless you've a servicer worker doing that (basically forcing a PWA). Are you sure you don't have some sort of caching method somewhere enabled? 3rd party extension maybe? There isn't any reason for it to just sometimes work as it's a simple REGEXP check for the shortcode. Are any other shortcodes doing this? Try [username] and see if it breaks as well.

This is on my local dev server and there is no other caching.

I actually already have another cb field on the  page: [cb:userdata field="name" user="###" /] - and it is always processed.  I attach the code I wrote for the articles.

Is it displaying on 1 view, but not another. For example feature articles it doesn't display but navigating to the article it does? This could purely be a content context issue. Have you made any changes to the settings in "Content - CB Gallery" Joomla plugin? As it's responsible for displaying inline galleries like that. So far I haven't been able to replicate your issue.